1. Field of the Invention
The present invention relates generally to a solid state color camera, and is directed more particularly to a solid state color camera using a CCD.
2. Description of the Prior Art
When a CCD is used as a camera, input light informations from an object are converted into electrical signals by being sampled at every picture element. Therefore, as opposed to the operation of well-known vidicon tubes, an output signal obtained from sampling every picture element is obtained from the CCD. That is, in the case that the sampling frequency is taken as f.sub.c (if the pitch of picture elements in the horizontal direction of the CCD is taken as .tau..sub.H, the sampling frequency f.sub.c becomes 1/.tau..sub.H), an output video signal S.sub.Y, which is obtained during one horizontal period when the respective picture elements are scanned at every horizontal period, includes, a DC component S.sub.DC of a luminance signal S.sub.Y and a side band component S.sub.M (AC component) which is produced in such a manner that the sampling frequency f.sub.c, as a carrier, is modulated with the DC component S.sub.DC, as shown in FIG. 1. FIG. 1, however, shows only the fundamental wave thereof. In this case, side bands are extended to lower and upper sides of the side band component S.sub.M having the sampling frequency f.sub.c as the center. If the band of the DC component S.sub.DC is selected sufficiently wide so as to avoid any deterioration of resolution, the side band component of the sampling frequency f.sub.c is overlapped on a high band component S.sub.DH of the DC component S.sub.DC as shown in FIG. 1. Thus, a part with hatches in FIG. 1 is produced as a sampling error. If a picture is reproduced under such a state, the sampling error appears in the reproduced picture as a flicker. In FIG. 1, S.sub.DL indicates a low band component of the DC component S.sub.DC.
Since the flicker is caused by the sampling error, if the band width of the DC component S.sub.DC is limited to, for example, smaller than one half of the sampling frequency f.sub.c, the sampling error will not be produced and hence the flicker on the reproduced picture can be avoided. However, the limitation of the band width of the DC component S.sub.DC accompanies with deterioration of resolution, so that it is not so preferred to limit the band width of the DC component S.sub.DC. For the band width of the DC component S.sub.DC to be selected without deteriorating the resolution (for example, about 3.5 MHz in this embodiment) and to avoid sampling error, it is sufficient to select a high sampling frequency.
Since the sampling frequency f.sub.c is the product of n and f.sub.H (f.sub.c =n.multidot.f.sub.H), where n is the number of horizontal picture elements in the CCD and f.sub.H the horizontal scanning frequency (practically, effective scanning time in the horizontal scanning direction is taken in consideration), when the sampling frequency f.sub.c is selected high to avoid the occurrence of sampling error as described above, it is required to increase the number, n, of picture elements, which causes the CCD to be difficult to manufacture.